Prime Minister Tony Abbott says his four-nation trip has been "constructive" and reinforced Australia's global position.
Mr Abbott has met with leaders in Indonesia, France, Canada and the United States ahead of hosting the G20 summit in November.
He wrapped up the trip with a visit to a medical research centre in Houston before heading home via Hawaii, where he will lay a wreath at Pearl Harbour and meet with Pacific Command officials.
Mr Abbott said his focus had been on trade, jobs and security.
"It's been a very constructive visit," he said.
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The two key announcements were the Force Posture Agreement - which will allow for a greater and more permanent presence of US Marines, aircraft and ships in Australia over the next 25 years - and a new consulate-general in Houston, where many Australian resources companies are based.
"We are significant, even a substantial, middle power," the prime minister said.
"We should use our weight in the world for our own good, for the good of our friends and allies and neighbours."
