Trump can fight until his face turns blue, he still does not have dictatorial powers to initiate spending bills. That power belongs to ONLY the House of Representatives, per US Constitution.
If the congress critters are hell bent on denying funds for the wall, the best POTUS can do is veto the spending bill. Then either the congress OVERRIDES his veto -or- the government comes to a screeching halt from lack of authorized funding.
Sometimes I wish we were under a benevolent dictatorship, such as in history by Mustafa Kemal Atatürk of Turkey, emperor Ashoka of the Maurya dynasty in India, or the Chinese emperor who built the 22,000 mile long wall which still stands after a millennium and served the purpose of stopping invaders from Mongolia.
Are you afraid of a shutdown over border wall funding?
I’m not.