Shipping companies like UPS and FedEx do have services available where they will clear the shipment across the border and deliver to the amazon FBA destination.

It will cost extra: currently 30% Trump tarrif on your Chinese goods (subject to change with little notice) plus the shipping companies clearance fee. You will have to do the math to see if selling on amazon.com is still profitable with the extra up-front costs.

Doing FBM on amazon.com will not be much easier since Trump's tarrif will apply to all made-in-China goods worth more than $0.00 -- the $800 diminis is gone (just on China made products for the moment, but products made in rest of the world will also be hit by 2027). The one FBM advantage in this mess, is that the extra border cost will occur when you have an actual sale to cover the expense. But you will need to figure if it is still profitable to ship the product (with tarrifs prepaid) direct to your Buyer -- however, the trouble with that is Trump's rapid changes to the tarrif / fee structure means what worked last week might not work this week -- so FBA is more stable for cost management.