But there is some support from USA at this moment, right?

Limited. There are 1) some sanctions on Russia 2) intelligence support (which Trump has withheld intermittently) and 3) allowing European countries to pay for US weapons to be sent to Ukraine. 4) Maybe I forgot something.

If the US completely stopped supporting Ukraine tomorrow it would be suboptimal, but wouldn’t really change the situation fundamentally. If the EU stopped tomorrow, Ukraine would be completely fucked, and Russia would win within 6 months.