It would make sense to send in your engineers first. Hard to send fighting forces when there is no infrastructure to support, house or feed them. There may have been 'space available', given the number of casualties amongst the British and French forces, but not for the numbers that Wilson said he was sending over.
This was probably viewed as overkill by our allies...they just wanted the troops to fill the causality gaps in their armies. Pershing trashed that idea very quickly.
"No man's life, liberty, or property is safe, while Congress is in session." Mark Twain