Whenever any city or village annexes all the territory within the boundaries of any road improvement district organized under sections 39-1601 to 39-1636.01, the district shall merge with the city or village and the city or village shall succeed to all the property and property rights of every kind, contracts, obligations, and choses in action of every kind, held by or belonging to the district, and the city or village shall be liable for and recognize, assume, and carry out all valid contracts and obligations of the district. All taxes, assessments, claims, and demands of every kind due or owing to the district shall be paid to and collected by the city or village. Any special assessments which the district was authorized to levy, assess, relevy, or reassess, but which were not levied, assessed, relevied, or reassessed, at the time of the merger, for improvements made by it or in the process of construction or contracted for may be levied, assessed, relevied, or reassessed by the annexing city or village to the same extent as the district may have levied or assessed but for the merger. Nothing in this section shall authorize the annexing city or village to revoke any resolution, order, or finding made by the district in regard to special benefits or increase any assessments made by the district, but such city or village shall be bound by all such findings or orders and assessments to the same extent as the district would be bound. No district so annexed shall have power to levy any special assessments after the effective date of such annexation.