The first responsibility of any government is to defend and to protect its own citizens.
There is no obligation, in law or common law or even by inference, for any government to defend the aspirations of people who are nationals of other countries, or to prioritize those aspirations over the aspirations of its own citizens.
From time to time governments may decide to assist foreign nationals, as the United States did in some of our foreign wars. But this is the exception, not the rule. And even these interventions did not prioritize foreign nationals over our own citizens.
President Trump is restoring common sense and sanity to a government which had lost its way. The American people never voted for open borders, for globalism, and for the surrender of their national sovereignty.
Successive administrations — both Republican and Democrat, functioning more like a UniParty than opposing parties — have gradually dismantled essential components of our national sovereignty. We know how this was done: trade deals which favored multinational corporations over U.S. citizens, shipping jobs overseas, ignoring the ever-growing illegal alien population (now estimated to be in excess of 20,000,000) which has driven down wages and expropriated entire sectors of the economy (i.e., meat packing, landscaping, etc).