Trump used a common racist cliché, regularly used against non-white people, against four non-white people. He told four non-white American citizens, three of which were born in America, to go back to their countries.
Now I know what you're going to say. "But he didn't say go back to your countries.... because you're not white." However, we both know you're only saying that because you don't want to admit Trump was being racial.
If a person tells Jews that the Holocaust didn't happen, we know that person is being anti-semitic because that's a common anti-semitic trope. If a person calls Italians a bunch of mobsters, we know that person is being racist because that's a common racist trope used against Italians. You don't have to mention a person's race to be racist.
And, as mentioned before, Trump has never told his white enemies to go back to their countries.