Solved with a CTE.

With AcctTrav as (Select * from Accounts where Jdx = 180)
Merge into AcctTrav a
Using TTN5563 t
On t.TaxID = a.TaxID

That didn't work I removed the "and jdx = 180" from the "When not matched by Source" portion and it deleted rows that were not 180.

I think I figured it out.

Merge into Accounts a
Using TTN5563 t
On t.TaxID = a.TaxID 
And a.jdx = 180