I was wondering what period of time was represented on your chart so here's the paper to your chart:
According to the United Nations [1], the United States has the highest number of immigrants (foreign-born individuals; see definitions in Box), with 48 million in 2015, five times more than in Saudi Arabia (11 million) and six times more than in Canada (7.6 million) (Figure 1). However, in proportion to their population size, these two countries have significantly more immigrants: 34% and 21%, respectively, versus 15% in the United States. Looking at the ratio of immigrants to the total population, countries with a high proportion of immigrants can be divided into five groups

1)
• The first group comprises countries that are sparsely populated but have abundant oil resources, where immigrants sometimes outnumber the native-born population. In 2015, the world’s highest proportions of immigrants were found in this group: United Arab Emirates (87%), Kuwait (73%), Qatar (68%), Saudi Arabia, Bahrain, and Oman, where the proportion ranges from 34% to 51%.
• The second group consists of very small territories, microstates, often with special tax rules: Macao (57%), Monaco (55%), and Singapore (46%).
• The third group is made up of nations formerly designated as “new countries”, which cover vast territories but are still sparsely populated: Australia (28%) and Canada (21%).
• The fourth group, which is similar to the third in terms of mode of development, is that of Western industrial democracies, in which the proportion of immigrants generally ranges from 9% to 17%: Austria (17%), Sweden (16%), United States (15%), United Kingdom (13%), Spain (13%), Germany (12%), France (12%), the Netherlands (12%), Belgium (11%), and Italy (10%).
• The fifth group includes the so-called “countries of first asylum”, which receive massive flows of refugees due to conflicts in a neighbouring country. For example, at the end of 2015, more than one million Syrian and Iraqi refugees were living in Lebanon, representing the equivalent of 20% of its population, and around 400,000 refugees from Sudan were living in Chad (3% of its population).
Small countries have higher proportions of immigrants
With 29% of immigrants, Switzerland is ahead of the United States and France, while the proportion in Luxembourg is even higher (46%). Both the attractiveness and size of the country play a role. The smaller thecountry, the higher its probable proportion of foreign- born residents. Conversely, the larger the country, the smaller this proportion is likely to be. In 2015, India had 0.4% of immigrants and China 0.07%. However, if each Chinese province were an independent country – a dozen provinces have more than 50 million inhabitants, and three of them (Guangdong, Shandong, and Henan) have about 100 million – the proportion of immigrants would be much higher, given that migration from province to province, which has increased in scale over recent years, would be counted as international and not internal migration. Conversely, if the European Union formed a single country, the share of immigrants would decrease considerably, since citizens of one EU country living in another would no longer be counted. The relative scale of the two types of migration – internal and international – is thus strongly linked to the way the territory is divided into separate nations.
A country’s proportion of immigrants reflects the scale of past immigration flows. The United States, with 15% of its population in 2015 born abroad (48 million people), is the top-ranking host country for migrants, despite its imposing quotas by nation, which considerably curtailed flows from 1924 to 1965. The United States is still an immigration country, and net migration (the difference between migrant arrivals and departures) was estimated at slightly above one million people in 2015 [1].
In these countries, the immigrant population was formed gradually over the years. Whether they come to work or to reunite with a relative, many migrants remain in the country of destination. They start a family, raise their children, grow old, etc. Other immigrants go back to their home country or move elsewhere. The immigrant population residing in a host country thus represents the population formed through successive immigration waves, minus the losses due to departures and deaths.
According to the United Nations [1], there were 258 million immigrants in 2017, representing only a small minority of the world population (3.4%); the vast majority of people live in their country of birth. The proportion of immigrants has only slightly increased over recent decades (30 years ago, in 1990, it was 2.9%, and 55 years ago, in 1965, it was 2.3%). It has probably changed only slightly in 100 years.
So it seems that pretty much the U.S. is going along like it has been; the proportion of immigrants hasn't changed much in 100 years. So who's panicking, exactly?