Hoagland arrived in Uzbekistan on July 23 for consultations with the country's leadership.
The diplomat told reporters that the US State Department was aware that there is a belief that countries neighboring Afghanistan are threatened, but does not agree with this assessment.
The Taliban has built up activities on the Afghani-Tajik border in recent months, triggering fears of the militants' advance to Central Asia. According to data from the non-profit International Crisis Group, about 500 Uzbeks and 300 Kyrgyz joined the ranks of the Islamic State militant group in Iraq and Syria in the past several years.
US-led NATO combat forces withdrew from Afghanistan in December 2014 after more than a decade of war.
In March, US President Barack Obama said all remaining US military bases in the country would be closed by the end of 2016.