I dont understand the assumption that Ukraine will do whatever some moron like Trump instructs them to do
What exactly do you want Ukraine to do without American aid?
To resource last year's failed offensive, Europe largely drained its own stocks of weapons. Some countries did it in exchange for American promises to make up for those transfers, by supplying new equipment in the future. Others did it without waiting for assurances regarding replacements.
So much equipment was transferred to Ukraine, that it's military quickly became larger than any NATO army, with the exception of Turkey and the United States.
More tanks than France, Britain, and Germany combined. More artillery systems than exist in all of Europe. More armored combat vehicles than exist on the balance of any European army. More MANPADS, more ATGMS, and so on and so forth. The only area where Ukraine is still behind is aircraft. However, 100+ F-16s have already been committed.
America chipped into the effort through drawdowns on their demobilized stocks, but didn't leave itself bare like many European states did. In fact, when the topic of transferring something to Ukraine from active inventories would come up - America always decided against it.
It will take years for Europe to build back up what they gifted to Ukraine. Without American aid, there is simply not a whole lot Europe can provide in 2025-2027.
Zelensky can ignore Trump, but only for so long. Sooner or later, without sufficient supplies, Ukraine will have to transition to trading men for time (some argue they are already in this state).