This explains the procedure of what it will take to get both of the House Resolutions passed through the US Senate, and what roadblocks and delays there could be as the strike date approaches...

"Both House-passed resolutions—with resolutions having the same effect as legislation, and each applying to most Class I railroads and their 12 labor unions—now proceed to the Senate where passage will be trickier, owing to that chamber’s unique parliamentary rules."

https://www.railwayage.com/regulatory/strike-averting-legislation-now-under-way/