Nichols and Tillman offer the view that political considerations meant that Washington based policy makers prohibited the use of some naval options, such as mining the North Vietnamese ports, greater use of naval gunfire and an amphibious landing North of the DMZ were ruled out.
Perhaps this restraint was justified considering the Cold War situation, however.....
Most of the war supplies for the communists were imported by sea. Therefore if a serious effort (mining, interdiction of ships carrying arms by US warships) has been made to stop this early on in the war, the outcome may have been changed. An amphibious landing North of the DMZ would have given the US/South Vietnam the initiative, cut communist supply routes and brought Hanoi to the negotiating table. I understand that many US Navy and US Marine officers felt frustrated with these options being ruled out.
Conclusion: Sea power (including carrier aviation) may have a strategic effect on the course of a conflict if used correctly. This is frequently ignored by politicians, media commentators etc, but needs to be remembered in a world where something like 90% of nations have coastlines.