This question might be more suitable for r/historicalwhatif.

The military forces of the United States were deployed around the world during the Cold War in order to "contain" the threat of Communism. As a result, a majority of combat ready forces were deployed in West Germany and Europe, rather than Southeast Asia.

Redeploying these troops from Europe to Asia would open a rather large gap for the Warsaw Pact to steamroll through.

To address your question, the short answer is yes.

George Veith's book, "Black April," looks at primary source documents from the North and South Vietnamese commanders. Both sides acknowledge the sheer firepower of American air support, as well as the crucial role of US supplies to the ARVN.

The issue is not the numbers of American troops deployed in-theater, but how they are used and if Vietnamization is increased. By the Easter Offensive, the ARVN had showed they were a competant fighting force under the right commanders and with enough equipment and support.

If the US had committed more strategic and tactical air power, and more logistical support, as well as beginning Vietnamization earlier, many of the ARVN commanders concluded that the war could be fought to a stalemate on the South's terms. Even the NVA commanders were fearful of what US air support could do to their forces during the Spring Offensive.